Method of applying a dye liquor to a tow

ABSTRACT

A method of applying a dye liquor to a tow wherein the tow is passed through a confined zone and a stream of the dye liquor is forced transversely through the tow at a minimum rate at least as great as   WHERE X IS THE DYE LIQUOR FLOW RATE IN GALLONS PER MINUTE, T2 is the thickness of the stream of dye liquor in inches, W is the width of the confined zone in inches, h is the thickness of the confined zone in inches, N is the number of filaments in the tow, Mu is the viscosity of the dye liquor in pounds per foot-second and Rho is the density of the dye liquor in pounds per cubic foot. Preferably, the dye liquor is forced through the tow at a rate at least 2 times the minimum rate.

United States Patent m1 Bittle et al.

[ 51 Sept. 23, 1975 TO A TOW Inventors:

Assignee:

Filed:

METHOD OF APPLYING A DYE LIQUOR David F. Bittle, Decatur, Ala.;

Arnold L. McPeters, Raleigh, NC.

Monsanto Company, St. Louis, Mo.

July 10, 1973 Related US. Application Data Continuation-impart of Ser. No. 260,622, June 7,

1972, abandoned, which is a continuation-inpart of Ser. No. 51,090, June 30, 1970, abandoned.

US. Cl. 8/177 R; 8/151.1; 8/177 AB Int. CL D061 5/70 Field of Search 8/151.2, 177

References Cited UNITED STATES PATENTS Williams 8/l5l.2 Cresswelli... 68/18l.1 R

Williams .7 8/151 X Reichle et al 8/151.2 Taylor 68/181 R Primary Examiner-Donald Levy Attorney, Agent. or Firm-Robert L. Broad, Jr.

[57] ABSTRACT A method of applying a dye liquor to a tow wherein the tow is passed through a confined zone and a stream of the dye liquor is forced transversely through the tow at a minimum rate at least as great as II p where x is the dye liquor flow rate in gallons per minute, T is the thickness of the stream of dye liquor in inches, W is the width of the confined zone in inches, 11 is the thickness of the confined zone in inches. N is the number of filaments in the tow, u is the viscosity of the dye liquor in pounds per foot-second and p is the density of the dye liquor in pounds per cubic foot. Preferably, the dye liquor is forced through the tow at a rate at least 2 times the minimum rate.

10 Claims, 3 Drawing Figures US Patent Sept. 23,1975 3,907,498

FIG. 2.

METHOD OF APPLYING A DYE LIQUOR TO A TOW This is a continuation-impart of application Ser. No. 260,622 filed June 7, I972 and now abandoned. for Method Of Applying A Dye Liquor To A Tow in the names of David F. Bittle and Arnold L. McPeters. which application was a continuatin-in-part of application Ser. No. l,()90 and now abandoned. filed June 30, l97(),for Method of Applying A Dye Liquor To A Tow" in the names of David F. Bittle and Arnold L. McPeters.

BACKGROUND OF THE INVENTION The dyeing of wet spun filaments in the gel form during fiber production eliminates several processing steps necessary when the fiber is first produced and then subsequently stock dyed. The elimination of these steps reduces the cost of the dyed fiber, so that gel state dyeing offers a real economic advantage. However, the prior art methods of continuously dyeing a freshly spun tow of filaments such as acrylic have not been entirely safisfactory. Some of the problems involved in this ap proach are inadequate dye takeup in the limited space and contact time practical on a spinning line, poor dye uniformity on the thousands of'filamen'tsin a commercial tow, excessive dye losses and the cost and complexity of adding a continuous dyeing step into the spinning line. With this in mind, one of the objects of this invention is to provide a novel and improved method of applying a dye liquor to a tow of filaments.

Another object of this invention is to provide a method of applying a dye liquor to a tow of freshly spun filaments in such a manner that dye takeup and dye uniformity are good and dye losses are low.

A further object of this invention is to provide a method of applying a dye liquor to a tow of continuous filaments in such a manner that the filaments are dyed to the desired shade within a very short contact time.

The objects of this invention are achieved by passing tow to be dyed through a confined zone and forcing a dye liquor transversely through the tow in the confined zone at a rate in excess of a predetermined critical value, the dye liquor being maintained at a temperature within a predetermined range. The critical minimum rate at which the dye liquor is passed to the tow must be at least as great as l WN x 3,0001" V T where x is the dye liquor flow rate in gallons per minute, T is the thickness of the dye liquor stream in inches, W is the width of the confined zone and the liquor stream in inches, h is the thickness of the confinedzone in inches, N is the number of filaments in the tow, p. is the viscosity of the dye liquor in pounds per footsecond and p is the density of the dye liquor in pounds per cubic foot. Preferably, the dye liquor is forced through the tow at a rate at least two times as great as the critical minimumrate.

Other objects and advantages of the invention will become apparent when the following detailed description is read in conjunction with the appended drawing, in which:

FIG. 1 is a. diagrammatic longitudinal cross sectional view of a dye applicator useful for carrying out the process of the present invention,

FIG. 2 is a cross sectional view taken along line 22 of FIG. lshowing the cross sectional area'of the confined zone in the dye applicator through which the tow is passed. and

FIG. 3 is a diagrammatic view of apparatus used with the dye applicator in carrying outthe process of the present invention.

Referring now in detail to the drawing there is shown, in a more or less diagrammatic manner, a dye applicator 10, which is useful in carrying out the method of the present invention. The apparatus is made up of upper and lower units 11 and l2which are held in a spaced relationship byside plates 13 (FIG. 2), the side plates 13 being secured to the upper and lower units 11 and 12 by screws 14. The space between the upper and lower-unitsll' and 12 forms a confined zone through which a tow 15 passes. The lower'face 18 of the upper unit and the upper face 19 of the lower unit 12 and the inner faces 20 of the side plates 13 form openings 23 through which the tow 15 passes as it enters and leaves the confined zone. The cross sectional area of the openings 23 is best shown in FIG. 2 and where h is the height or thickness of the opening 23 and W is the width of the opening. The cross sectional area of each of the openings 23 is that cross sectional areawhich the tow is free to assume as it enters and exits from the applicator.

The lower unit 12 is provided with an inlet 21 through which a conventional dye.liquor is applied to the tow. The inlet 21 extends across the lower unit 12 from one of the side plates 13 to the other. The inlet 21 has a thickness of AT T preferably being no greater than about lOh, where h is the thickness of the confined zone (as shown in FIG. 2), so as to concentrate the flow of the dye liquor through the tow 15 at one location. The value A is between 0.05 and 10. The upper unit 11 is provided with a recess or chamber 22 which receives the dye liquor passing through the tow 15 from the inlet 21. The length of the confined zone is the length of the chamber 22, as best shown in FIG. 1.

The chamber 22 directs the dye liquor back through the tow 15 at the openings or outlets 23 spaced from the inlet 21 in streams having a thickness T (refer to FIG. 1). The preferred value for the dimension T is within the range of 2h to 5h. The dye liquor entering the inlet 21 passes through the tow 15 and is divided into substantially equal parts which pass back through the tow 15 at the outlets 23. The chamber 22 completely fills with dye liquor under pressure. This pressure forces the dye liquor through the openings or outlets 23, and the tow 15, at a high velocity. As will be readily apparent from a study of FIGS. 1 and 2, the tow passing through the outlets will, because of its direction of travel, be free to assume a configuration having a cross sectional area of Wh, while the dye liquor exiting from the confined zone will be free to pass through an opening having the dimensions W and T As shown in FIG. 3, the dye applicator 10 is mounted over a vat 30 containing a conventional dye liquor 31. Spaced pairs of rolls 32 and 33 feed the tow 15 through the dye applicator 10 at a uniform speed. A pump 34 connected to the vat 30 and the inlet 21 of the applicator l0 pumps the dye liquor from the vat 30 through the applicator via the inlet 21. The dye liquor exiting from the applicator It) falls back into the vat 30 and is recirculated. The dye liquor is shown as droplets falling back in the vat. Actually, it will be a stream, rather than droplets. Additional dye may be fed to the vat 30 from a supply 38, the vat being provided with an overflow line 39 to maintain a constant depth in thevat. This will maintain the dye liquor at a uniform, desired dye concentration level. Pairs of stripper bars 36 positioned in contact with the tow as shown in FIG. 3 are used to prevent the dye liquor from flowing beyond the edges of the vat 30.

Any conventional dye liquor which is useful for conventional dyeing can be applied by the method of this invention. Those skilled in the .artare thoroughly familiar with dyes, dye liquor concentrations, which dyes are effective with various types of man-made fibers. etc.

The dye applicator may be located at any step of the spinning process after coagulation and before drying and collapsing of thefilaments. The length and dimen sions of the applicator may be varied. The composition ofthe dye liquor may be water or a solvent-water mixture with or without buffer salts, acids, retarding agents, or other materials customarily used in dyeing. Any wet spun fiber, dry spun fiber, or other swollen fiber can be dyed, provided that it is in a gel state.

The dye liquor makes one pass through the tow at each of the outlets 23, for a total of two passes at the outlet locations. Since twice as much dye liquor passes through the tow at the inlet 21 as at either of the outlets 23 it must be considered the dye liquor makes a double pass, or two passes, through thetow 15 at the'inlet 21. Thus,- in the apparatus shown the dye liquor may be -said to make four passes through the tow 15. The dye liquor can be deflected back and forth through-the tow as-many times as desired. At each point where the dye as set out above. 1f the dye liquor passes through the tow at a lower rate very little of the dye will be applied. to the tow. Preferably, the flow rate will be at least twice this rate. 7

Of course, a minor portion of the dye liquor will, in an applicator such as described above, not pass completely through the tow but will travel along the voids in the tow to the outlets 23. Since it would be very difficult to actually measurethe dye liquor flow rate inside the tow an easierway of determining whether the minimum critical flow rate is exceeded is desired. The flow rate into the inlet 21 can be measured and, since there are two outlets 23, should be at least twice without regard for actual flow rate in the tow or the fact ous dye liquor at various temperatures.

Temperature C. lbs/ftsec. lbs/cu.ft.

-Continued Temperature T, I lbs/ft-scc. lbs/cult.

35 4.115 x 10- 62.06 40 4.40 x 10' .,6l.95 4.02 x 10- 61.82 3.69 x 10" 61.68 3.-:0 10- 61.54 3.15 x 10- 61.38 2192 10" 61.22 .70 2.72 x 10 61.04 2.55 X 10- 60.86 x0 2.39 x 10- 60.67 ,85 2.25 x 10 60.47 00 2.12 x'10- 60.27 2.01 x 10- 60.06 1.90 x 10 59.113

EXAMPLE 1 .A conventionaldye liquor known to those skilled-in the art as-suitable for dyeing acrylic fibers was applied to a tow of filaments made up of 95% acrylonitrile and 5% vinyl acetate, the filaments being in a gel state. The tow contained 160,000 filaments of 18 denier each.

The cofined zone was 7.88 inches in length and had a width, W, of 6 inches. The dimension T was 0.63 inches and the dimension h was 0.34 inches. Critical minimum flow rate'of the dye liquor through the outlets 23, at a temperature of 50C.., was 19.2 gallons per minute with the preferred critical minimum being 38.4 gallons per minute. Actual flow of the dye liquor was maintained within the range of 50 to 70 gallons per minute. Dye liquor temperature was 50C. The speed of the towwas such that the dwell time of the tow in the confined zone was 1.45 seconds. The tow was dyed to "a uniform, deep shade. Various other conventional dye solutions were applied in a like manner. All were successful.

EXAMPLE 11 A conventional dye liquor was applied to a gel-state acrylic tow containing 160,000 filaments made up of 95% acrylonitrile and 5% vinyl acetate, the'filament denier being 18.

gallons per minute. The towhad a dwell time in the confined zone of 0.95 seconds. All of the filaments in the tow were dyed toa deep, uniform shade.

EXAMPLE 111 A conventional'dye liquor was applied was applied at 50C to a tow of modacrylic filaments in gel state, the tow containing 18,000 filaments of denier each. The confined zone of the dye applicator was 5.22 inches in length and had a width, W, of 3.5 inches. The dimension T was 0.57 inches and the dimension h was 0.22 inches. The critical minimum flow rate through the outlets was 5.7 gallons per minute with a preferred minimum of 11.4 gallons per minute. The dye liquor was circulated through the confined zone at a rate within the range of 30 to 40 gallons per minute. The

tow had a dwell time of 2 seconds in the confined zone. h is 3/32 inch All of the filaments in the tow were dyed to a uniform, N is 1000 deep shade. p. is 3.15 X

p is 61.39 EXAMPLE IV 5 A 160,000 filament acrylic tow was dyed in gel State, Actual dye liquor flow rate through the applicator using a conventional dye liquor, in a dye applicator was 0.21 gallons per minute, in excess of the critical having a confined zone of the dimensions set out in Exminimum of 0,14 gallons per minute. ample with a y liquor temperature of the 10 The dye bath was made fresh for each run and anacritical minimum flow rate was 16.2 gallons per minute -lyzed After the tow was completely strung up on the with a preferred minimum rate of 32.4 gallons per min spinning line the dye bath circulation was started. No ute. The actual flow rate was held within the range of dye makeup was added during spinning, so that the dye to gallons per minute. The tow had a dwell ti e concentration decreased. Dyeing lasted 20 minutes on in the confined zone of 0.95 Seconds. All Of the filal5 each run. At the end of this time dye bath circulation ments in the tow were dyed to a uniform, deep shade.

EXAMPLE V tion utilizing anapplicator such as described above.

Run

was stopped. The final concentration and dye concentration in the wash bath were then determined. The dye pickup on the last portion of dyed fiber was also determined by dissolving the fiber in solvent. All dye determinations were made by absorption measurements on a Cary Model 14 Spectrophotometer in a well known manner. The tow was evaluated visually for dyeing uniformity.

Dye Applicator lmmersion Length, inches Dye Bath Temperature, C. Circulation Rate, gal/min Original, /1

After 20 minutes, 7(

Decrease Dye on Fiber, "/1 by wt.

End of 20 minutes Pickup Ratio:

Dye Lost in Wash Bath After 20 Minutes, gms Tow Color Uniformity Runs 2 and 3 were dyed during immersion in a conventional dip bath with the bath flow countercurrent to tow movement. In all cases the aqueous dye liquor was recirculated from a separate dye tank. A commercial basic dye, Sevron Red GL, C.l. Basic Red 18, was used for all three runs. The dye liquor was aqueous and had a temperature of 60C. Free dye was washed from each tow after the dyeing operation.

The cross-sectional area of the tow passageway, or confined zone, through the applicator was 0.00875 square inches. The dimensions W and h were both 3/32 inch. The dimension T (refer to FIG. 1) was 9/32 inch.

The critical minimum flow rate of dye liquor at 60C.

where T, is 9/32 inch W is 3/32 inch Two indicators of dyeing effectiveness are the decrease in dye bath concentration during 20 minutes dyeing and the dye pickup ratio at a specified time. Both show that the process of this invention gave much higher dye pickup even though the conventional dip baths were 54% longer. A comparison of Runs 1 and 2 where the initial dye bath concentrations were equal shows 4.3 times as large a decrease in dye bath concentration with this invention. The dye pickup ratio was 6-8 times higher with this invention.

Dye pickup in the dip bath application can be increased by going to the higher dye bath concentration as in Run 3 but dye losses will be increased proportionately as shown.

The process of this invention gave a very uniformly dyed tow with no filament-to-filament color differences. In contrast, both runs dyed in the conventional dip bath were quite streaky.

EXAMPLE VI Twelve parts of a 50% acrylonitrile/50% methyl vinyl pyridine copolymer was blended with 88 parts of a acrylonitrile/5% vinyl acetate copolymer. The resulting polymer blend was dissolved in dimethylacetamide to form an 18% solids spinning dope. The methylvinyl pyridine provided amino groups making this polymer dyeable with acid dyes.

This dope was spun into fiber and the tow dyed in accordance with Run 1 of Example V except that the tow contained only 250 filaments. The critical minimum dye liquor flow rate, with a tow of 250 filaments, was

0.069 gallons per minute, with a preferred minimum of 5 0.138 gallons per minute. Actual dye liquor flow rate .was 0.21 gallons per minute. No stretch was applied to the tow in the applicator.

Liquid carryover of the tow entering the dye applicator was 380%. An acid dye, Scarlet 4RA, C.1. Acid Red 18, No. 16255, was used for this run. The dye liquor was prepared using sodium formate and formic acid to adjust the pH to 2.5. Samples of the dye liquor and fiber were taken simultaneously at the end of the run for dye analysis.

Dye Liquor Temperature: 50C.

Circulation Rate: 0.21 gallons per minute Percent Dye in Dye Liquor: .052

Percent Dye on Fiber: 1.53

The color uniformity of this tow was very good.

EXAMPLE V11 A polyacrylonitrile polymer was dissolved in dimethylsulfoxide to form a solids dope. This dope was spun into fiber and a tow made up of 250 filaments was dyed as in Example V1.

Another basic dyestuff, Astrazon Yellow 7GLL was used for this sample. Pickup results are shown below.

Dye Bath Temperature 50C. Circulation Rate: 0.21 gal/min. Dye on Fiber: 2.53 Dye in Bath: 0.97

2.53 Pickup Ratio. 097 26 Polyacrylonitrile fibers are known to be very difficult to dye in conventional stock dyeing. With the process of this invention dyeing is achieved easily and uniformly on the gel state fiber.

EXAMPLE VIII A 93% acrylonitrile-7% vinyl acetate copolymer with an n of 0.154 was dissolved in dimethylacetamide to form a solids spinning dope. The dope. The dope was extruded into a spin bath containing 55% dimethylacetamide/45% water to form a tow of 1,000 filaments and drawn onto a godet at 17.5 fpm.

This tow was passed directly through the dye applicator described in Example V without washing to remove 'the solvent, dimethylacetamide. The dye liquor had the Dye Liquor.Temperature: 38C.

Circulation Rate: 0.21 gal/min.

The effectivenss of this process in a solvent-water dyeing system is apparent. Also,-a ll samples were uniformly dyed even at these very light shades.

EXAMPLE 1X A terpolymer of 7.4% vinyl acetate. 2.4% vinyl bromide and 91.2% acrylonitrile with an n, of=0.15 was dissolved in dimethylacetamide to form a 25% solids spinning dope. This dope was extruded through a 60 hole, 5 mil hole size spinnerette into a 60% dimethylacetamide/40%- H O spin bath at 30C. The 60 filament tow was drawn onto a godet at 17.5 fpm, washed with'water during 15 wraps on this godet and passed directly through the dye applicator of Example V. Liquid carryover into the dye bath under these conditions was over 230% based on dry fiber. From the dye applicator the tow passed to a second godet whose speed was varied. The tow also dipped into a neutralization bath of 0.5% NaHCO underneath this godet. The tow was then stretched 6.0X in a boiling water cascade, finish applied, and the tow dried, crimped, and relaxed as customary in the spinning process. Final denier per filament in this case was 15.0.

Four runs were spun with variations in dye bath temperature. Sevron Red GL dye stuff was used for these experiments. Results are tabulated below. Fresh dye liquor was prepared before each run and no' dye was added duringthe 10 minute run time.

In this example an apparatus such as. that described above was used for carrying out the process of the invention with the exception that the apparatus was made larger to accommodate larger tows. The confined passageway through the apparatus had a width, W, of 4.0 inches and a height, h of 11/64 inch. The thickness, AT of the stream of dye liquor impinging on the tow at the inlet 21 was l /sinches, while the dimension T Conditions Polymer Composition )3 percent acrylonitrile 7 percent vinyl acetate Number of filaments 40,000

Polymer n 0.16 Polymer solvent-solids dimethylacetamide -25'% Spin bath temperature 35 C.

Stretch in applicator l Spin hath composition 55% dimethylaeetamide/ 45% water Dye Liquor Tow Speed through Dye TemperatureC. Applicator ft/min. Uniformity 30 l8 Fair 40 18 Good S 18 Excellent 60 I8 Excellent 70 27 Excellent 80 27 Excellent 90 27 Fair I00 27 Streaky What is claimed is: l. The method of applying a dye liquor to a tow of filaments, comprising a. advancing the tow through a chamber, said chamber having an opening at each end thereof for the passage of tow into and out of the chamber and for the passage of a dye liquor out of the chamber, passing said dye liquor through the two in a direction countercurrent to the tow at one of the openings and concurrent with the tow at the other opening, filling the openings at the ends of the chamber with said tow filled with dye liquor, and

b. forcing a dye liquor into the chamber at a point between the openings in the chamber to fill the chamber with dye liquor and force said dye liquor through the tow and out of the chamber at said openings, said dye liquor being forced into the chamber at such a rate that the dye liquor flow rate outward through each of the openings in the chamber is at least WN II p where x is the dye liquor flow rate in gallons per minutc. T is the thickness in inches of the dye liquor stream flowing through each opening, W is the width in inches of each said dye liquor stream and the tow. h is the thickness in inches of the tow passing through said openings, N is the number of filaments in the tow, p. is the viscosity of the dye liquor in pounds per footsecond, and p is the density of the dye liquor in pounds per cubic foot.

2. The method of claim 1 wherein the dye liquor flow rate is at least twice as great as l WN 3.00015 T 3. The method of claim 2 wherein the dye liquor makes at least four passes through the tow.

4. The method of claim 2 wherein the dye is circulated from a dye liquor supply to maintain the dye concentration of said supply at a constant predetermined valuev 5. The method of claim 2 wherein the dye liquor forced through the tow is deflected to pass back through the tow at a plurality of locations along the tow.

6. The method of claim 2 wherein the dye liquor is at a temperature within the range of 30C. to C.

7. The method of claim 2 wherein the dye liquor is at a temperature within the range of 50C. to 100C.

8. The method of claim 2 wherein the tow is composed of acrylic filaments.

9. The method of claim 2 wherein the tow is composed of polyacrylonitrile filaments.

10. The method of claim 2 wherein the tow is composed of modacrylic filaments. 

1. THE METHOD OF APPLYING A DYE TO A TOW OF FILAMENTS, COMPRISING A. ADVANCING THE TOW THROUGH A CHAMBER, SAID CHAMBER HAVING AN OPENING AT EACH END THEREOF FOR THE PASSAGE OF TOW INTO AND OUT OF THE AMBER AND FOR THE PASAGE OF A DYE LIQUOR OUT CHAMBER, PASSING SAID DYE LIQUOR THROUGH THE TWO IN A DIRECTION COUNTERCURRENT TO THE TOW AT ONE OF THE OPENINGS AND CONCURRENT WITH THE TOW AT THE OTHER OPENING, FILLING THE OPENINGS AT THE ENDS OF THE CHAMBER WITH SAID TOW FILLED WITH DYE LIQUOR, AND B. FORCING A DYE LIQUOR INTO THE CHAMBER AT A POINT BETWEEN THE OPENINGS IN THE CHAMBER TO FILL THE CHAMBER WITH DYE LIQUOR AND FORCE SAID DYE LIQUOR THROUGH THE TOW AND OUT OF THE CHAMBER AT SAID OPENINGS, SAID DYE LIQUOR BEING FORCED INTO THE CHAMBER AT SUCH A RATE THAT THE DYE LIQUOR FLOW RATE OUTWARD THROUGH EACH OF THE OPENINGS IN THE CHAMBER IS AT LEAST X=3000T2((WN/H)(U/P))XX(1/2) WHERE X IS THE DYE LIQUOR FLOW RATE IN GALLONS PE MINUTE, T2 IS THE THICKNESS IN INCHES OF THE DYE LIQUOR STREAM FLOWING THROUGH EACH OPENING, W IS THE WIDTH IN INCH OF EACH SAID DYE LIQUOR STREAM AND THE TOW, H IS THE THICKNESS IN INCH OF THE TOW PASSING THROUGH SAID OPENINGS, N IS THE NUMBER OF FILAMENTS IN THE TOW, U IS THE VISCOSITY OF THE DYE LIQUOR IN POUNDS PER FOOT-SECOND, AND P IS THE DENSITY OF THE LIQUIR IN POUNDS PER CUBIC FOOT.
 2. The method of claim 1 wherein the dye liquor flow rate is at least twice as great as
 3. The method of claim 2 wherein the dye liquor makes at least four passes through the tow.
 4. The method of claim 2 wherein the dye is circulated from a dye liquor supply to maintain the dye concentration of said supply at a constant predetermined value.
 5. The method of claim 2 wherein the dye liquor forced through the tow is deflected to pass back through the tow at a plurality of locations along the tow.
 6. The method of claim 2 wherein the dye liquor is at a temperature within the range of 30*C. to 100*C.
 7. The method of claim 2 wherein the dye liquor is at a temperature within the range of 50*C. to 100*C.
 8. The method of claim 2 wherein the tow is composed of acrylic filaments.
 9. The method of claim 2 wherein the tow is composed of polyacrylonitrile filaments.
 10. The method of claim 2 wherein the tow is composed of modacrylic filaments. 